Method for making ceramic articles



Nov. 4, 1969 J. R. DREVER ET AL 3,476,847

METHOD FOR MAKING CERAMIC ARTICLES Original Filed Oct. 5, 1966 2 Sheets-Sheet l United States Patent Int. Cl. B28b 21/06 US. Cl. 264-102 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method for making ceramic articles such as pouring tubes. Fine particles are mixed in a, liquid to form a slurry. This slurry is subjected to a vacuum. The slurry is then pumped into a moldfor the ceramic article. Heat is applied internally of the mold to set the slurry. The interior of the mold is then chilled until it contracts fromthe article. The article and external portion of the mold is lifted from around the internal portion of the mold and is then heated to permit extraction of the formed article from the mold exterior portion.

This application is a continuation of our copending application Ser. No. 584,561, filed Oct. 5, 1966, now abandoned, and entitled Method for Making Ceramic Articles.

This invention relates generally to a method for making ceramic articles and more particularly to a method for making a ceramic pouring tube of the type employed in pressure casing operations.

Such an operation is described in United States Patent No. 2,874,424, wherein molten metal disposed within a container is forced by the application of fluid pressure from the container through a pouring tube into a mold disposed outside of the container. The pouring tubes commonly employed in pressure casing operations of this type are generally formed from a refractory such as an alumina-silica, as for example mullite.

It is an object of this invention to provide a method for making ceramic articles. I

A further object of this invention is to provide a method for making pouring tubes for pressure casting operations.

These and other objects and advantages of this invention will become apparent from a reading of the following detailed description of this invention when taken in conjunction with the drawings wherein:

FIGURE 1 is a schematic illustration of the apparatus of this invention with the mold in filling position;

FIGURE 2 is a schematic illustration of a portion of the apparatus of this invention with the mold in curing position;

FIGURE 3 is an elevational view partially in cross section of the mold apparatus of this invention; and

FIGURE 4 is an elevational view of the mold apparatus of this invention.

Referring now to the drawings, reference numeral denotes a mixing tank into which the various ingredients are introduced. The tank 10 is provided with a motordriven blade mixer (not shown). An outlet 12 controlled by a valve 14 is provided on tank 10 in order that the contents thereof may be removed and dumped into a pouring tank 16. The tank 16 is provided with an airtight cover '18 through which the outlet pipe 12 extends. A frusto-conical outlet 20 is provided on the bottom of the pouring tank 16, which outlet 20 is connected by suitable means to a filling hose 22.

The pouring tank 16 is provided with means such as an air vibrator 24 to vibrate the contents of the pouring tank. It is also provided with a vacuum line 26 which is connected to a conventional vacuum pump 28 through valve 30 in order that a vacuum may be applied to the interior of the tank 16. In addition, an air pressure line 32 is connected to the tank 16 for forcing the contents out of the tank through hose 22. The air inlet line 32 is connected to a source of air pressure such as a compressor 34 which is controlled by a regulator 36 and a valve 38.

The hose 22 is connected at its end remote from the pouring tank outlet 20 to the pouring tube mold 40 in order that the contents of the tank 16 may be forced into the mold 40. A quick disconnect 42 is secured to the end of the hose 22 to facilitate rapid connection to the mold 40. The end of the mold 40 remote from its inlet is provided with an air escape hole (not shown) to permit escape of any air entrapped within the mold 40. It is also provided with an air operated vibrator 46 connected to air line 44 to provide slight vibration to the mold 40 during its filling.

Referring now to FIGURE 2, wherein the mold 40 is shown in its inverted position, the mold cover or base 48 is provided with a water inlet 50 and a water outlet 52. The water inlet 50 is connected to a source of hot water such as a heater 54 and a pump 56 by the line 58 Which is controlled by a valve 60. It is also connected to a source of cold water (not shown) by cold water line 62 controlled by valve 64. Hot water line 58 and cold Water line 62 are connected by a T joint 66 and thus to inlet 50 by line 68 The water outlet 52 is connected to a water return line 70. Cold water passing through return line 70 is drained off through line 72 controlled by valve 74 and connected to line 70 of T joint 76. Hot water is returned to a surge tank 78 by line 80 controlled by valve 82. The line 80 is also connected to the water return line 70 by the T joint 76.

Referring now to FIGURES 3 and 4, the mold 40 is rotatably mounted on supports 84. The supports 84 are provided with bushings 86 having rotatably mounted therein trunnions 88 which are in turn fixedly secured to a mold support frame 90. The frame 90 is provided with an opening 94 on either side of the mold 40 to receive mold trunnions 92. In the position shown in FIGURE 3, the mold trunnions rest on braces 96 and are prevented from accidental dislodgement by locking pins 98 extending through slots 100 on opposite sides of the frame elements 102.

The mold 40 consists of an aluminum base plate member 102 which in a position shown in FIGURE 3 rests in a recess 104 machined in the cover 48. Member 102 is provided at its periphery with an annular ring member 106 provided with bayonet mounting slots 108 as best shown in FIGURE 4. A hollow aluminum core 110 is positioned in annular recess 112 of cover 48. The core 110 extends upwardly as shown in FIGURE 3 through an opening 114 in member 102. The outer diameter of core 110 forms the inner diameter of the pouring tube which will be manufactured in the mold 40. A water tight seal is provided around the outer periphery of the lower end 116 of the core 110 by an O-ring 118. The upper end 120 of the core 110 is sealed by a cone-shaped sealing member 122 which is sealed at its outer periphery by an O-ring 124 surrounding member 122 and positioned within the inner portion of the core 110.

A water drain pipe 126 is centered within the interior of the core 110. Drain pipe 126 at its lower end 128 is in open communication with the water outlet 52 in cover 48. The upper end 130 of pipe 126 is open to the interior of core 110. The pipe 126 is held in position by an eye bolt 132 extending downwardly through sealing member 122. A pin 134 extends through the eye 136 of eye bolt 132 and through opposite sides of the drain pipe 126. A- nut 138 holds the eye bolt in place on sealing member 122.

A hollow steel cylinder 140 surrounds the core .110 and is spaced therefrom to provide mold cavity 168. The interior surface 142 of the cylinder 140 is smooth and free from irregularities, which surface 142 defines the outer diameter of the pouring tube to be manufactured in the mold .40. The cylinder 140 is secured at its lower end 144 to the ring member 106 by bayonet mountings 146 which are locked in place in slots 108. The cylinder 140 is centered around the core 110 and is maintained in this position by three centering pins 148 which are positioned 120 apart and extend between the outer peripheryof the core 110 and the inner surface 142 of the cylinder 140. The pins 148 are positioned near the upper end 150 of the cylinder 140.

The upper end 150 is closed by a cone-shaped cover 152and is locked into place on the end 150 by bayonet mountings 154 which are locked in place in slots 156 on the lower end 158 of the cover 152. A steel tube 160 is attached to the upper end 162 of the cover 152. The quick disconnect 42 is positioned on the open end of the tube 160. A slide cut-off 164 is provided in the tube 160 intermediate the cover 152 and the quick disconnect 42. To assist assembling and disassembling of the mold 40, hooks 166 are provided on opposite sides of the exterior of cylinder 140 near the upper end 150.

In operation, the mold 40 is assembled in the position shown in FIGURE 3 and is then rotated to its position shown in FIGURE 4. The hose 22 is not yet connected to the quick disconnect 42 but is placed in the position shown by dotted lines in FIGURE 1.

The solid ceramic particles which will form the pouring tube are dumped into the mixing tank 10, which tank contains water, colloidal silica and ice. The composition of materials utilized to produce the pouring tube are disclosed in our copending application entitled Composition for Making Refractory Articles, filed Oct. 5, 1966, and having Ser. No. 584,365 now abandoned. The batch in the tank is stirred by the blade mixer (not shown) until a slurry is produced having the consistency of frothy mud. The ice is added in order that the batch after completion of mixing will have a temperature of around 6 to 25 C. After completion of mixing, the pouring tank is vacuumized by vacuum pump 28 to a vacuum pressure in the neighborhood 28 of mercury.

Valve 14 between pouring tank 16 and mixing tank 10 is opened to allow the slurry in the tank 10 to trickle to the bottom of the pouring tank 16. This results in removal .of substantially all air bubbles from the slurry. After the tank 10 is emptied and the air is removed from the slurry, the hose 22 is connected to the quick disoonnect 42. Air pressure is then supplied to the tank 16 through line 32 from compressor 34. This forces the slurry out of the bottom of tank through hose 22 into the mold 40 where it fills the mold cavity 168, which cavity is formed between the core 110 and the cylinder 140.

During the filling of the mold, which is in it position shown in FIGURE 4, the air vibrator 46 is turned on. As soon as the cavity 168 is filled with the slurry, the slide Shut-Off 164 is actuated to shut off flow of the slurry into themold. The air control valve 38 is shut off to release the pressure in pouring tank 16. The hose 22 is disconnected from quick disconnect 42 and the mold 40 is again rotated to its position shown in FIGURES 2 and 3. The cover 152 is removed and any slurry surrounding the seal 122 is also removed. A thin film of oil or water is applied to the top of the slurry to prevent loss of moisture during curing of the slurry.

Water inlet'SO is connected to water line 68 and water outlet is connected to the water drain line 70. The hot water pump 56 is started and vlave 60 is opened. The cold water valve 64 is in its closed position. Hot water at-about- 60 6. is pumped through -line-58 and- 'line 68 into water inlet 50 which is in open communication with the interior of core member 110. The water circulates upwardly through the core 110 and drains downwardly through drain pipe 126' and is piped out of the mold 40, through water outlet. 5 2. and returned to the tank. .78 by way of water drain line 70 and .hot water drain line; 80. The. heat provid ed ..by the water :causes the colloidal silica to gel, which takes between and 70 minutes to accomplish. e e,

The pump. 56' is then shut olf, w' alvebtl is'closed and valve 64 is opened. Cold watertitabout- '15 "c1, is 'theri pumped through line 62 and line .6 8,. into the mold and circulated therethrough as with the hot vvz itenwValve 82 is closed and valve 74 in the cold water drain line 72 is opened to permit drainage of'the'cold water from the mold 40. The cold water causes 1116 aluminum core member 110 to shrink away from the pouring tube 170. At thisp'o'int the cold water circulation is" stopped and liftihg 'means (not shown) is attached to'the books 166 to lift "cylinder 140 to which is attached ring 106 and plate member 102 off of cover 48'. Thepouring tube 170 which is: resting on plate member 102 'is thus lifted'fromiar' o the core member 110. This assembly is then placedin a dryer maintained a'tabout 80 C. where it is held 'there from6to40ho'urs.

The assembly is then removed from the dryer and the cylinder 140 is disconnected from the ring 106 and stripped from the tube 170. The shrinkage of the tube during drying permits the easy removal of the cylinder 140 from the tube. Thereafter the tube is fired in a kiln at about 2600" F. for about three days.

It can be seen from the foregoing that this method,

and apparatus provides an efiicientprocedure for producing ceramic articles such as pouring tubes for bottom pressure casting. A i

We claim:

1. In a method of making a ceramic tube the steps of mixing fine particles in a liquid to form a slurry, then placing the slurry in a chamber, then connecting the bottom of the chamber to the bottom of an upright pipe having its upper end closed by a releasably attached airvented annulus within a central openingof which is snugly fitted a downwardly projecting closed inner pipe spaced from the first-mentioned pipe, then .pressurizing the chamber to force the slurry upwardly between thelpip es until the first-mentioned pipe is filled with said slurry,

I then inverting the pipes and heating the slurry until it has set to form said tube, then chilling the inner pipe until it contracts from said tube, then lifting the firstmentioned pipe and said annulus to draw the tube from said inner pipe, and then heating the tube and firstmentioned pipe until the latter has expanded from said tube, and then releasing the annulus from the firstmentioned pipe and drawing the first-mentioned pipe from the tube.

2. A method according to claim 1 wherein the slurry is subjected to a vacuum while in said chamber.

3. In a method of making a ceramic tube the steps of mixingfine particles in a liquid to form a slurry, then trickling the slurry downwardly through a chamber while subjecting the slurry and chamber to vacuum at a value sufiicient to de-air the slurry, then connecting the bottom of the chamber to the bottom of an upright pipe having its upper end closed by a releasably attached air-vented annulus within a central opening of which is snugly fitted a downwardly projecting closed inner pipe spaced from the first-mentioned pipe, then pressu'rizing' the chamber above the slurry to act on its upper'surfaceahd thereby force the slurry upwardly btwe en the pipes until the first-mentioned pipe is filled with 's'aid' slurry,

then cutting off flow ofslurry to and-from the bottom of the first-mentioned pipe, then disconnectingthe first mentioned pipe from the chamber, then inverting the pipes and heating the inner pipe to heat the slurry until 2,008,339 7/1935 Ruml. it has set to form said tube, then chilling the inner pipe 2,298,446 10/1942 White 25-420 until it contracts from said tube, then lifting the first- 2,485,857 10/1949 Bower. mentioned pipe and said annulus to draw the tube from 3,160,931 12/1964 Leach. said inner pipe, and then heating the tube and firstmentioned pipe until the latter has expanded from said 5 FOREIGN T tube, and then releasing the annulus from the first-men- 365,290 1/1932 Great m tioned pipe and drawing the first-mentioned pipe from the 456,550 11/1936 Great Bntamtub e References Cited 10 ROBERT F. WHITE, Primary Examiner U D STATES PATENTS K. J. HOVET, Assistant Examiner 500,675 7/1893 Schnell. X R.

1,315,733 9/1919 Massey. 1,363,912 12/1920 Pauly 15 25128;264327,333 334 

